Christianity and tarot make very odd bedfellows indeed. One might even say they need separate bedrooms at the very least. That opinion is held not only by many Christians but also by many Pagans and neo-pagans who reject the Christian symbolism in the cards and claim the symbology to be corrupted forms of earlier pagan symbolism. While they have a valid point, I think it's interesting that both Christian and Pagan belief systems reject the Christian historical roots of tarot.
The Church took offense with the deck almost immediately. Card playing had associations with gambling ever since playing cards had been introduced to Europe and various laws and decrees were enacted to discourage that. However, the earliest known disparagement of tarot cards specifically comes from an anonymously penned sermon, known as "The Steele Sermon" or "Sermones de Ludo cum Aliis," c. 1480. This sermon detailed the Trumps of tarot and asserts that the Trumps were invented and named by the Devil and as such hotly discourages their use. The blasphemous depiction of The Pope, the inclusion of a female Popesse, the imagery of The Devil, The Tower and so forth created objections and banning by the Church. But it likely wasn't just the pictures that caused such a ruckus. The politics of the time were more than probably the driving force behind the opposition.
The characters in the tarot "triumph" or trumps were seen in the many Roman Catholic pageantry processions, not too unlike what we see preceeding Lent at Mardis Gras and Carnival. These pageants were evangelistic devices of the Church designed to convert. Indeed, the Church has used various forms of earlier pagan imagery in its quest to convert the heathen, so the imagery these pageants used were designed to place the Christian story in a pagan context. As the Reformation took hold in Europe, these pageants disappeared from France, Italy, and England. All religious plays were banned in France in the mid 1500's and with them went much of the historical truth about what those original tarot trumps actually represented. A very sad loss, indeed.
While we may have lost much of the original intention and meanings of the trump cards, we have not lost the association with the demonic first set forth by that frothing friar. The Reformation did nothing to change that, in fact under John Calvin the Church government at Geneva instituted what amounted to a theocracy that strictly governed personal and household conduct, severely punishing those that deviated. Card playing under Calvin's regime was not allowed. (However, this was not the case in Germany where Luther's Reformation did not specifically prohibit card playing, so the making and playing of cards continued, as it does today.) My point here is there has always been a gap between what the Church proscribes and what its followers actually do. While the Catholic church, both pre-Reformation and post, linked tarot with the devil, your average tarocchi playing parishoner most likely dismissed that notion out of hand.
Today, modern Christian fundamentalist sects likewise attempt to place the fear of God in its followers regarding the use of tarot, but their reasons are somewhat different. As tarot developed through the centuries it became embraced by Christian mystical secret societies such as the Order of the Golden Dawn and its splinter groups. These societies attached occult and esoteric meanings and uses for the cards apart from their game-playing use. All three major monotheistic religions, Judaism, Christianity, and Islam forbid the practice of divination. Well, sort of. Officially they do, anyway. All three have their esoteric branches: The Jewish Kaballah, Christian Hermeticism and Gnostic Mysticism, and Islamic Sufism, for example. These are the woo-woo branches of these religions and often utilize divination practices in a quest for spiritual enlightenment. However, the more mainline of these religions don't trust that stuff and pretty much dismiss most of it. Conservative and fundamentalist Christian groups commonly reject tarot as belonging to the kind of divination that is forbidden in the Bible and view it as a doorway through which demonic forces can enter your life and send you reeling down into the depths of depravity. It's hard to take that kind of attitude seriously from the same types of folks who also claim the devil inhabits children's toys, games, and dolls.
However, I'm not going to play tarot apologist here and attempt to make a case that tarot was originally Christian in origin and therefore ought to gain the stamp of approval from Christians. I could, but there just isn't enough known about the origins of tarot for me to do that. There certainly is very blatant Christian iconography in tarot images, but without those original pageantry plays and meanings, it's difficult to assume just what the cards were projecting. Moreover, I just don't want to. Certainly there was a time in my life when I Biblically prooftexted just about everything I said and did, but I'm not in that place any longer, thank God. Apparently certain people in Church leadership have always had an issue with the cards while others have not. That being the case, as it always has been, it lies with the individual to decide whether or not practicing tarot reading is in line with or counter to their faith. Many tarot readers are Christians, some even incline towards a conservative bent. One reader I am acquainted with is married to a pastor and is herself a member in the ultra conservative denomination The Church of Christ. I've seen enough divination practiced within Christian circles to know that it isn't divination per se that is objected to, but the manner in which it is done and with which tools.
Christianity and the tarot have a marriage that has been rocky and uncomfortable at best, but the images clearly cannot be divorced from their Christian context. It is true that the early Church did indeed co-opt many of the pagan traditions, symbolism, and festivals and layered upon them a Christian filter and interpretation in order to convert the masses. Therefore the symbolism within tarot does have origins that predate Christianity, but the Christian meaning is intended to be a part of that symbolic language as well. The creators of those images were likely well indoctrinated into the "new" meanings as well as the old, a blending which, to this day, is difficult to separate out. It's a fascinating study to research the way the same symbols have been used by various cultures and groups, and to watch them morph through the centuries taking on layer upon layer of meaning. Tarot crams so many of these symbols into 78 cards that they should keep one busy for a very long time. In any case, no matter how you may feel about the joining of Christianity with tarot, they are inextricably bound and it helps to understand more about the tense history this union has endured.
Mystic Flower by Gustave Moreau c.1875
Mystical Origins of the Tarot: From Ancient Roots to Modern Usage by Paul Huson